HDDs, SSDs, NASes and Cloud Storage: Making sense of them

October 13, 2014

HDD, SSD, NAS, Cloud Storage. What do they mean?

The information world is a much bigger place than it was some years ago. Not only do we have easy access to terabytes of data at our fingertips, we now have various mediums in which we get access to them. The technical jargon and acronyms can get a little daunting sometimes, but don’t worry–we’ll try to make it easy to understand for you in this article.


The hard disk drive (HDD) has been a mainstay of computing for the past two decades. Most of you should be pretty familiar with them, and chances are that your system contains at least one of them. HDD storage is really cheap today, too: the cost-per-gigabyte is about just 4.5 cents per gigabyte! 1TB drives are mainstream, and 4TB drives are not out of reach for most.

HDDs typically come in two form factors: 3.5-inch and 2.5-inch. 3.5-inch HDDs are generally faster, though with energy savings being a priority these days, some may spin at roughly the same speeds of 2.5-inch HDDs. 2.5-inch HDDs generally spin more slowly and may thus appear to be more sluggish. 2.5-inch HDDs are used in laptops as well as in USB hard drives today.

In HDDs, data is basically stored on magnetic platters. A read-and-write head sits at one end of the HDD, and when retrieving or storing information, the platters spin so that the relevant area on the magnetic platter is in-line with the head to be read from and written to. This spinning and seeking takes time, which is why accessing small, random data is often slower than when accessing large chunks of data which are usually at the same place.

As HDDs are a spinning, magnetic medium, they are somewhat volatile and may fail from time to time. Thankfully, all HDDs today come a diagnostic tool (available on the manufacturer’s website) which you can download to assess the health of your HDD. Bad sectors are a typical sign of a failing hard drive. If you see these numbers growing over time, or start hearing loud noises from your HDD, you should send it in or purchase a replacement.

Since HDDs rely on spinning to retrieve data, random access speeds (such as when copying or reading many small files) are usually quite slow, whereas sequential speeds (such as when copying or reading a large file) in a defragmented system is very quick.


The solid-state drive (SSD) seeks to correct some of the shortcomings of HDDs. They rely on flash storage, and as such are pretty similar to thumbdrives, except that they are much faster and much more durable. Since there’s no spinning required, there’s no risk of failure due to moving parts. Thus, they are much more hardy: a drop will probably not cause you to lose precious data.

Random access speeds are really quick, since there’s no need to spin to various places just to retrieve data. This is why they are popular as system drives. When an operating system boots up, lots of small files require to be loaded. This takes a considerable amount of time on a traditional HDD which has to actively spin and seek, but for a SSD such data retrieval is much faster.

Why, then, have they not replaced HDDs completely? The first reason is due to cost. Cost-per-gigabyte is about 45 cents per gigabyte today. For the price of a 256GB SSD, you can probably purchase a 2TB hard drive instead. Therefore, in many desktop systems, enthusiast choose to use SSD to store their main operating system and important files and rely on HDDs, either internal or external, to store files that are not used as often.

Another reason is due to durability. I believe SSDs are far more reliable than HDDs, but all SSDs eventually fail. This is because the memory has limited write cycles. However, based on typical usage, your SSD can probably last you between 10 to 30 years or more. By then, chances are that you won’t be using the same SSD anyway. Manufacturers usually have a (usually conservative) mean-time-before-failure rating that shows how much total data you can write on their SSD.


The Network-attached Storage (NAS) is quite simply an external hard drive connected over your home network. There are a few reasons for the emergence of NASes.

One is that routers are ubiquitous in households today. NASes could either interface with your router wirelessly or through an Ethernet port. Once set up, your other computers using the same router can seamlessly access data on the NAS, just as if it was a local hard drive. If you work in an office, chances are you’ve already been exposed to NASes before. Remember that central hard drive which everybody can access on their computers, typically with a drive letter starting with “N”? That’s likely to be a NAS.

The other reason is perhaps linked to what we have discussed earlier. HDDs can store lots of data cheaply, and SSDs store less and are faster. Many people use laptops (which contain either a fixed-sized HDD or a SSD) and other mobile devices (which use a variant of SSDs and have small storage space anyway), so they have to find a way to store data that can’t fit into their hard drives. The NAS is a convenient solution, for you can easily place a large hard drive that all your devices can access from at home.

Home NASes are not that expensive these days. If you don’t want to get your hands dirty at all, opting for one from a HDD manufacturer such as Western Digital could be a wise choice.

Otherwise, you could also opt for a diskless enclosure from, say, Synology and add in your own hard drives. Many of these NASes have multiple drive bays to improve redundancy, so you won’t have to worry even if one hard drive fails.

The main drawback of NASes is its speed. Thankfully, with fast wireless technologies and the proliferation of Gigabit LAN in routers today, it’s not so much of an issue now. Day-to-day usage such as playing back your multimedia files from NASes shouldn’t be an issue: they should be quick enough.

Cloud Storage

Last but not least, we arrive at cloud storage, which seems to be the buzzword these days. Apple has them in the form of iCloud, Microsoft in the form of OneDrive, and Google in the form of Google Drive. There are also other popular options such as Dropbox. I won’t go through the intricacies of different cloud providers here–perhaps that’s reserved for another article–but just an overview of what it is.

Cloud storage basically takes NASes out of your home network and onto the Internet. You won’t need to manage or maintain them, for the storage provider does that for you. The main upside is that you can easily access them wherever you go, as long as you’re connected to the Internet.

It’s device-agnostic as well: your desktop, laptop, tablet and smartphone will be able to access them. You won’t have to worry about your HDD crashing because there’s a backup available on the cloud. It also means that you won’t have to waste precious space on your local hard drive as you can store them on the cloud instead.

Cloud storage has its shortcomings too. Not everyone has access to fast Internet speeds, and as such, retrieving a file from the cloud could be much slower than if it were locally or on your home network.

The next is a lack of control: you may be kept wondering if your data is still there, or if it has been stolen or deleted. Just recently, iCloud accounts of several celebrities were hacked into and their personal photos released on the world wide web. Thus, really personal data should be kept off the cloud as much as possible.


Now that we have covered the basics of the four main types of storage today, I hope it has given you a more in-depth understanding of them. Each has their pros and cons, and chances are that we use more than one of these storage mediums today.

Perhaps an ideal home would be one where everyone has their own personal computer with either a SSD or HDD inside, which, together with their smartphone, is hooked up to their router where they can access common files on the NAS system. And then when they leave home for work or school, they can still access certain data (e.g. documents, pictures and music) from the cloud.

Being on a budget doesn’t mean you have to skimp on these things. A terabyte hard drive is easily available for about $55. You can get a small-sized SSD to pair it with your hard drive. Some manufacturers offer a hybrid hard drive, with about 32GB of SSD storage and 500GB or 1TB of HDD storage, potentially offering the best of both worlds.

Cloud storage, too, is often free if your needs are basic. OneDrive offers 15GB of free storage, for example. NASes, too, are not luxury items if you know where to look. For me, I managed to find a diskless Buffalo Linkstation Live for just $25. Paired with an old hard disk, I get an entry-level NAS costing next to nothing.

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